With a recent significant improvement in the reproduced sound quality of audio equipment, a large power supply circuit, which was once regarded to be of poor economy and technically disadvantageous, has once again been taken into account for audio equipment. The introduction of high-quality wire material, particularly oxygen-free copper wire, linear-large-crystal oxygen-free copper wire and the like, for a signal conductor of audio signal circuits, has come to be recognized as indispensable. Even when most of the generally known methods of improving the sound quality, as described above, are adopted, however, it is pointed out not only by those skilled in the art but also by a number of enthusiastic users, that there still remains a delicate difference between the original sound and the reproduced sound, which difference can be discriminated by the human ear.
Generally, in order to further improve the reproduced sound quality, various attempts have hitherto been made with respect mainly to the material used in the signal circuits of audio equipment, as described above. In addition, to prevent a signal current flowing through a signal conductor from being adversely affected by an external electromagnetic field, it has been considered that the signal conductor should be shielded as completely as possible by means of a shielding member. On the other hand, as far as the inventor knows, the fact that undesirable influences, such as increase in the distortion of the signal current, are caused by the shielding member has not been completely recognized, and therefore, no particular attention has been paid to eliminate the undesirable influences.
If it is assumed to be possible to practically neglect the undesirable influences caused by the external electromagnetic field, then it is obvious that the shield member can be dispensed with, and a bare signal conductor can be used. However, such a use environment is quite uncommon and extraordinary. Consequently, provision of a shielding member for the signal conductor of domestic-use audio equipment has been regarded as being indispensable.